The general field of this invention is the art of U-bolt saddle clamps which are conventionally employed in the exhaust systems and elsewhere in automobiles and trucks powered by internal combustion engines.
The prior art in this field is for the most part derived from a basic assembly comprising a U-shaped bolt threaded at its ends having a semicircular bight portion integrally connecting a pair of parallel legs which mount in axially slidable relation a sheet steel saddle member including tubular portions receiving and housing the bolt legs and connected by a central web extending transversely between the tubular housings and being integral therewith. The saddle usually has a pipe engaging arcuate face having a curve with the same radius as the U-bolt. Nuts are fitted on the threaded free end portions of the bolt legs which are then torqued against the adjacent ends of the tubular housings to bring the saddle and bolt together for tightly clamping a coupling of telescoped cylindrical tubes disposed between the bight of the U-bolt and the arcuate edge of the saddle member. Lock washers are sometimes interposed between the nuts and the ends of the tubular housings.
Typical examples of prior art clamp structures of this general type are illustrated by Riker U.S. Pat. No. 2,719,345; Osborn et al., U.S. Pat. No. 3,137,053; Dowling et al. U.S. Pat. 3,772,745; and Heckethorn U.S. Pat. No. 3,955,250. In these devices the saddles are formed from initially planar oblong blanks of relatively thin sheet steel. These sheets are cut, stamped and rolled or otherwise formed to provide a central web integrally connecting a pair of tubular portions arranged to slide axially on the legs of an associated U-bolt. In some cases the saddle web is formed of only a single sheet thickness; in others, such as Heckethorn, the web is formed from a pair of identical sheets joined in parallel full face contact or in laterally spaced relation as in Downing, U.S. Pat. No. 3,729,782.
In modern usage, the work or pipe engaging edge of the saddle is required to impart sufficient clamping pressure on the pipe sections to indent a semicircular bead therein. The applied clamping pressure is a function of the torque level to which the securing nuts are finally tightened when they are drawn up on the threaded ends of the U-bolt legs. Tests have shown that in prior art clamps such as Riker where the saddle webs have no longitudinal reinforcement, the saddles start to twist laterally and roll over when tightened to torque levels approaching 20 foot lbs. Clamp saddles longitudinally reinforced such as Dowling et al. successfully resist such twisting and rolling at much higher torque levels, such as 30 foot lbs. Even more rigid clamps are shown in Heckethorn U.S. Pat. No. 3,955,250 and Heckethorn Ser. No. 796,217, filed May 12, 1977, now patent no.
Double saddle U-bolt clamps have been designed and used inthe past, as for example Graham et al. U.S. Pat. No. 2,959,834; Downing, supra; and Brewer 4,063,700; however one of these are designed to provide a substantially 360.degree. pipe indentation now required to obviate separation of the pipes and to ensure gas tightness. In all cases of known double saddle clamps, each saddle may, under adequate torque, impress a separate groove, not in the same plane as the U-bolt.